An apparently suicidal man turned on a natural-gas source at a Bay Park home Tuesday, sending flammable fumes wafting through and outside the structure and prompting authorities to evacuate nearby residences while trying to contact him.

Police said a crisis intervention expert was able to talk to the man, but he cut off contact and stopped answering his phone. The standoff continued for four hours before police searched the home and could find no signs of the individual.

A robotic device was sent in to try and find him, then SWAT teams entered.

The incident began when police got an emergency call about 11:30 a.m. from a someone reporting the man’s threats to kill himself at a house in the 1400 block of Galveston Street, SDPD public-affairs Officer Matt Tortorella said.

Arriving patrol personnel detected a strong presence of natural gas in the air around the home and began clearing people out of surrounding residences. Fire department personnel, meanwhile, cut off the supply of gas to the house where the man was holed up.